Zinc lozenges are associated with shortening the duration of common cold episodes by up to 40%, according to research. The evidence emerged from the combined results of 13 trials which tested the ability of zinc lozenges, which dissolve in the mouth and are widely available, to fight off colds. Three of the studies showed taking daily doses of zinc acetate higher than 75 milligrams - more than is generally recommended - as soon as symptoms began, shortened colds by an average of 42 per cent.